Automatic telephone system



Feb. 17. 1925.

M. LANGER AUTOMATIC TELEPHONE SYSTEM Filed Sept. 2, 1921 Patented Feb. 17, 1925.

UNITED STATES PATENT OFFICE.

MAX LANGEB, OF HERMSDOBF, NEAR BERLIN, GERMANY, ASSIGNOR 'IO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed September 2, 1921. Serial No. 498,178.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L., 1313.)

To all whomit may concern:

Be it known that 1, MAX LANGER, of Hermsdorf, near Berlin, Rodernstrasse 58, Germany, a German citizen, have invented 8 certain new and useful Improvements in Automatic Telephone Systems (for which I have filed applications in Germany, filed 23, 10, 1915, Pat. No. 300,949, granted December 28, 1916; Austria, filed 21, 10, 1916, 10 Pat. No. 75,594, granted February 28, 1918; Denmark, filed 4, 7, 1916, Ser. No. 926--16; Czechoslovakia, filed April 16, 1921, revalidation of Austrian Patent 75,594, granted MaylO, 1921), of which the following is a specification. v

The subject of the invention is a circuit arrangement for telephone systems with primary call seekers and secondary pre-selectors each call seeker and pre-selector forming a selecting pair and operating simulta neously. 7

.With such circuit arrangements it may occur that a pre-selector finds a free switching position (e. g. in automatic telephone systems a free first selector) before the call seeker associated with the pre-selector has completed its setting operation. The result of this is that, although the pre-selector has taken into use a free switching position and has marked it engaged, this position is again rendered free, because the speaking line has not been switched through at the call seeker and therefore the relays in the speaking line do not operate at the switching position, the result being that the same conditions exist as though the receiver had been replaced at the calling station at the end of the conversation. The switchin position being no longer markedengage the pre-selector is left free to advance further. This is followed by the disconnection of the test relay of the pre-selector; and since the switching position is now apparently free again, th1s relay can operate once more and the switching position may again be taken into use. This cycle is repeated until the call seeker has reached the calling line, or the line relays operate at the switching position. a On the other hand, a further rotation of the preselector to another free switching position may follow the first disconnection of the test relay, the pie-selector being then rereleasedagain and rotated furtherwhich operation may be repeated until the call seeker has completed its setting. It may also happen that during the re-energizing of the testing relay, the test relay of another preselector that is in motion and has just reached the switching position operates, whereby two calling subscribers may be connected up to one and the same switching positlon.

This defect is prevented according to the invention, by the arrangement that, when a free switching position is taken into use by a pre-selector, devices are brought into operation at the selecting pair for the time during which the call seeker associated with the pre-selector is still performing its setting movement, which devices block an engaged switching position and hold the pre-selector in the set position.

The drawing illustrates a circuit arrangement according to the invention, in which the selecting pair simultaneously started by the starting relay 0, consists of a call seeker AS acting as the primar pre-selector switch, and of a pre-selector V acting as the secondary pre-selector switch. The switching position taken into use by the pre-selector is marked engaged by a resistance w, which may be bridged across the two speaking leads. The circuit is so arranged that if the call seeker has completed its setting operation before the preselector has done so, the speaking leads will not be bridged by the resistance to. This resistance, which is preferably about equal to that of the calling subscribers line, is only connected up when the pre-selector has completed its setting sooner than the call seeker, and in fact as soon as the switching relay V operates at the call seeker to switch it through to the speaking line.

The arrangement operates in the following manner:

\Vhen the subscriber takes down his receiver at the calling station, the calling relay It operates and prepares at contact 1 a circuit for the cut-off relay T and for the test relay Pa of the call seeker. At the.

same time it closes at contact 2, a circuit for the starting relay C of the selecting pair (earth, batter relay C, contact 18, line 20, contact 2, earth) which at 3 connects up the rotary magnet D0. of the call seeker, and at 4: connects up the rotary mag net Do of the pre-selector VW, so that bot-h the call seeker AS and the pro-selector Vii i ba in to rotate. llliOlGU'VGl', by c osing the contact 5, the starting'relay (l prepares the circuit for energizing the test relay Pa and the cut-oil relay T, and at 6 it prepares the, circuit for energizing the test relay Po and the engaging relay Q. As soon as the call seeker AS reaches the calling line, the relays Pa and T operate (earth, battery, relay T,.contact 1, test wiper of the call seeker AS, test relay Pa, contact 5, earth). The cut-oil relay 'l, by opening contacts and 8, disconnects thecalling relay from the calling line, so that R releases and opens thecontacts 1 and 2. The cut-o1? relay T has however closed the contact 9, thereby locking itself and the test relay Pa, in a circuit independent of the calling relay it. The test relay Pa at contact 10 short-circuits its high-resistance winding, thus blockingthe calling line, and by opening the contact 11, breaks the circuit of the rotary magnet Da, so that the call seeker AS remains stationary. The test relay Pa also switches the line through at 12 and 13. As soon asthe pre-selector VW reaches a free primary selector GVJZ the testing relay Po and the engaging relay C operate (earth, battery, relay Po, contact 6, testing arm or the pro-selector VYJ, contact m, relay C normal contact H, earth). The tes "clay Po short circuits its high-resistance w ,ding at 1 1, and prevents the selector Girl being taken into use byanotherpro-selector. rrlso, by opening the contact 15, the test relay P2) disconnects the rotary magnet Do, so that the pre-selector is stopped. The test relays Pa, P2) at 16 and 1? connect up the switch ing relay V which at 19 switches the start ing lead through to the next pair of preselecting switches. By closing the contacts 21, 22, the relay V also switches the speaking line through, so that the line relays A, B at the selector Gi l are energized, the relay A being the impulse relay while relay B controls the release. At contact 23, the relay B keeps open the circuit of the release magnet M.

If, contrary to the foregoing assumption, the pre-selector is brought to a standstill sooner than the call seeker AS, then the resistance 10 is bridged across the speaking leads at 24, 25 by the relays C and 1%, so that the line relays A, ll enei 'zet (earth, battery, relay A, contact 7), pre-sclector Vl V, contact 24, resistance w, contact 25, pre-selector Vl V, contact 29, relay B, earth).

B opens at 28, the circuit for the release magnet M. When the call seeker AS subsequently reaches the calling line, the testing relay Pa operates and with the test relay P'v, connects up therelay V at 16 and 17.

Relay V at contact 18 disconnects the. starting relay C, which on dee'nergizing, opens its contact 2%, so that w is disconnected at the same time. However, since the relay V switches the speaking line through at 21, 22, the rel- B does not release.

It the bridge to were not connected up, the relays A. and B could not be energized when the pie-selector Vl V reaches the se lector Gil until the call seeker reached the calling line, and during that interval the following operations would take .ilace.

On the pie-selector reaching a free selector, the relays Po and C operate. C connects up the release magnet at 23c, and the latter by opening its contact m, breaks thecircuit 01'' P4) and C. The engaging rclay C again disconnects the release magnet M, so that the contact 1% again closes the circuit otC and Po and the cycle of operat ons is repeated. it now, during time i s operates anew, pic-selector" V W reaches the selector GWJ, the test relays Po of both pro-selectors operate at the same time, thus causin the selector to be taken into use from two directions and causing wrong connections.

l Vhat I claim and desire to protect by Letters Patent is: I v

.1. in a telephone system, a selector switch, talking conductors terminating in said switch, a hunting switch having line wipers for connecting with said conductors, means for thereafter connecting the conductors of a calling line with said wipers, and'means for bridging aid wipers until the calling line is connected.

2. In a telephone system, a selector switch, talking conductors terminating in said switch, a hunting switch having movable contacts for connecting with said conductors, means for operating said hunting switch over a calling line and for connecting the conductors of said line with said movable contacts, a line relay in said selector, a local circuit for said line relay closed over one of said talking conductors when the hunting switch is operated, a control circuit for said line relay closed when the calling line is connected to said movable contacts, and means for then opening said local circuit.

3. In a telephone system, a calling line, a switch, backward and forward 1 nting switches linked together and operat ng conten'iporaneously for connectin with said line and switch, respectively, talking conductors extending through said switches, and means in said forward hunting switch effective in case the said selector is found iirst for closing a bridge across the talking c -nductors.

in a telephone system, a calling line, a selector switch, backward and forward ha, tingswitches linked together and operating contemporaneously for connecting with said line and switch, respectively, talking conductors extending through said switches, means in said forward hunting switch eflective in case the said selector is found first for closing a bridge across the talking conductors, and means for opening said bridge when the calling line is found.

5. In a telephone system, a calling line, a selector switch, backward and forward hunting switches linked together and operating contemporaneously for connecting with said line and switch, respectively, a controlling line relay in said selector, and means in said forward hunting switch effective in case said selector is found first for closing a local circuit for said line relay.

6. In a telephone system, a calling line,

a selector switch, backward and forward hunting switches linked together and operating contemporaneously for connecting with said line and switch, respectively, a controlling line relay in said selector, means in said forward hunting switch effective in case said selector is found first for closing a local circuit for said line relay, and means effective when the calling line is found for substituting a new circuit including the calling line for said local circuit.

Signed by me at this 15th day of August, 1921.

MAX LANGER; In the presence of GUSTAV THICLE, HEINRICH EHWALD. 

